Here's a simple but reportedly effective way of producing a low cost electrically operated valve. He uses a standard hydraulic valve, driven by what he says is an electrically operated pepper mill to provide the actuation. I've not seen such a mill here but an electrically operated coffee grinder would probably do the same job (and just may be what this is)(but probably isn't). An electric battery powered screwdriver would also be suitable. Such have 2 or 3 stages of epicyclic gearboxes to allow a relatively modestly sized electric motor to produce the very substantial torque required to turn screws. Actuation speed will depend on gearing and voltage used. Performance is not mentioned on the web site but in an email to the ARocket list he says: > The 1/4" valve opens, at 50 bar, in 2/10 sec, on 9V. That's reasonably impressive. It may give the potato cannon people some ideas :-) - if they haven't been doing this sort of thing for years without me noticing. Russell _________________ On the site he says: This valve is the most recent I made. It's also the easiest to operate, probably the most reliable, and even though the cheapest. It's a 1/4" BSP hydraulic valve, connected to the mechanism of a cheap electric pepper mill (the kind you can buy at < $5). I made an aluminium frame that holds the two parts together; the torque is transmitted via a custom-made piece also. There is a small on/off switch that stops the motor when it has made a quarter of turn (not visible on the picture, it wasn't installed yet). One can probably replace it with a magnetic position sensor and thus get a throttleable valve. This and a pyro and servo operated vales described here: http://www.student.montefiore.ulg.ac.be/~teney/h2o2propulsion_actuatedvalves.htm Picture here: http://www.student.montefiore.ulg.ac.be/~teney/h2o2propulsion/electroactuatedvalve.jpg -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist